Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$165.61	6.264%	$175.9838	$175.98	$176.00	$176.00
Purchase #2	$40.41	7.128%	$43.2904	$43.29	$43.30	$43.30
Purchase #3	$197.47	12.730%	$222.6079	$222.61	$222.60	$222.60
Purchase #4	$80.87	3.861%	$83.9924	$83.99	$84.00	$84.00
Purchase #5	$34.88	13.291%	$39.5159	$39.52	$39.50	$39.50
Purchase #6	$152.43	4.613%	$159.4616	$159.46	$159.45	$159.50
Purchase #7	$65.94	10.478%	$72.8492	$72.85	$72.85	$72.80
7 purchase totals =	$737.61		$797.7012	$797.70	$797.70	$797.70